Elastomeric materials have long been used as gaskets, seals, sealing compounds and other like components of architectural structures, vehicles, appliances and other such articles of manufacture. For example, in the field of architecture, elastomeric architectural strips are used to cover joints between building sections, at rooflines and around windows, both in new construction and as a repair item for preexisting buildings. Silicone polymers are particularly important in the fabrication of architectural pre-cured seals. These polymers are extremely flexible and strong, and their inertness makes them resistant to oxidation and photodegradation. Silicone rubbers may be fabricated in a variety of colors by the inclusion of pigments therein, so as to match a variety of substrates.
A wide variety of elastomeric articles, such as architectural pre-cured seals, gaskets and the like are frequently prepared from silicones or other polymeric compositions by a process in which a polymer composition is extruded to provide a shaped body which is subsequently cured to produce the finished item. In the context of the present disclosure, an extrusion process is defined to include any forming process wherein a precursor of the elastomer is forced under pressure into or through a shaping member such as a die or a mold to produce the shaped body. A number of shaping processes are known in the prior art. For example, U.S. Pat. No. 4,783,289 discloses a continuous extrusion process for the preparation of elongated silicone rubber members. According to the process, a silicone composition is extruded from a die into a body of water to produce an elongated member, which passes through the body of water and cures while it is doing so
Elastomeric articles produced through extrusion processes of the prior art tend to cure with very smooth surface. In many instances, this smooth surface is not desirable in the article. For example, in architectural applications, it is generally desirable that joints and seals blend in with the appearance of the building, and the glossy surface of the elastomer contrasts strongly with the texture of stone, wood, concrete, stucco, metal and other such building materials. For reasons such as these, the prior art has made various efforts toward providing a matte and/or textured finish on extruded elastomeric items. For example, a textured finish can be provided to an item by curing the elastomer within a mold having a textured surface. This approach is impractical when very large, or long, items such as architectural pre-cured seals are being fabricated, or when the residence time of the article in the mold is a factor in the logistics or economics of the molding process. Other approaches include providing a textured surface by using a roller which forms the surface of the yet uncured compound, or by brushing, sanding or otherwise abrading the surface. These approaches require an additional processing step and is not always practical, particularly when the items being manufactured having large or complex, surfaces. In yet another approach, the finished articles are provided with a textured surface by overcoating them with another compatible material. Again, this requires a complicated post-processing step, and the technique often is not applicable when the item includes surface characteristics, which would be masked by the topcoat. This process is labor intensive and requires the precisely controlled extra process.
Other known attempts to create a texture within the silicone compound are less satisfactory than the present invention. In particular, attempts have been made to add sand to the silicone compound to add texture to the otherwise smooth surface. However, the sand adversely affects the silicone matrixes and results in a harder, less flexible material with reduced elastomeric properties crucial for construction use. Further, the range of textures is limited and less aesthetically pleasing. Another method for creating a surfaced texture to some degree (matte finish) is shown in U.S. Pat. No. 5,595,695. This process, of exposing the surface of the elastomer to humid atmosphere requires special equipment to cure the profile.
Thus, it will be appreciated that there is the need for a process by which elastomeric compounds, particularly silicone rubber elastomeric articles, having a textured finish may be fabricated. The process should not require any post-cure processing steps nor should it require any long residence time of the article in a shaping die or mold during the curing process. It is further desirable that any such technique be compatible with continuous fabrication processes such as those used for the extrusion of silicone rubber seals. It is also desirable that any such technique not requires extensive modification of presently employed processing equipment. Further, the process should be adaptable to rapid changes in the texture to be produced or the color of the material produced.
The use of silicone based sealant, is similarly well known in the construction industry. These types of products are commercially available from Dow Corning Corp., Midland, Mich.: DC732 Multi Purpose Sealant, DC790 Building Sealant, DC795 Building Sealant and from General Electric Comp., Waterford, N.Y.: GE1200, GE SilProof. These products are used to fill in or seal or conceal joints in construction, such as expansion joints in structural wall or floor members. These sealant or caulks are liquid or paste like (uncured) in storage but as they are hydrolyzable, will rapidly begin to cure when exposed to atmospheric humidity. These sealant are typically stored in tubes and are dispensed through a nozzle at one end of the tube by forcing the enclosing wall at the opposite end of the tube toward the nozzle. This form of application is well known in the industry, and utilizes an applicator commonly referred to as a caulk gun. When the sealant flows from the nozzle of the storage tube it typically forms a bead of a diameter dependent upon the diameter and cross section of the nozzle and upon the rate of application. This bead may then be manually formed to create a more aesthetically appealing appearance, as with a putty knife or finger. The bead, whether formed or not, will cure with a relatively smooth appearance, creating the same contrast with textured surfaces as discussed above. Thus, it is preferable to have a sealant, which will cure with a textured surface to blend in with the surrounding surface.
The present invention is directed to elastomeric compounds having a textured finish. The compound is particularly suited for the fabrication of silicone rubber articles and may be implemented in a continuous fabrication process, such as that used for the manufacture of elongated architectural pre-cured seals. The present invention also has significant artistic applications. The method for manufacturing the compound of the present invention is simple to implement and control, and yields high quality, textured finished, cured elastomeric articles.
The present invention allows a profile to be extruded with a texture without additional processing. The texture can be varied by varying the contents of the silicone substance extruded. The present invention also allows a sealant or filler to be produced that can be stored in liquid form or paste like form, applicable through ordinary caulk gun type applicators or other known application methods, and will cure with a textured surface.
These and other advantages of the present invention will be readily apparent from the drawings, discussions and description, which follow.